High frequency power amplifier module

Abstract

The present invention provides a power amplifier module used in a cellular phone or the like. In the power amplifier module, a bias control circuit converts a bias voltage to a current by MOS transistors, whereby a voltage drop is reduced and the value of the bias voltage is lowered. Bias control signals outputted from the bias control circuit are inputted to a high-frequency amplifying unit through low-pass filters. The low-pass filter comprises an inductance, and a condenser. Each of the condensers attenuates an envelope frequency. Each of the inductances suppresses a change in impedance at a carrier frequency of a modulation signal.

1. A high frequency power amplifier module, comprising:
 a first transistor which performs current amplification in response to an input signal received at a base terminal thereof, the base terminal being biased based on a first bias control signal; 
 a first bias control circuit having an input which receives a bias voltage and an output which generates the first bias control signal, wherein the first bias control circuit includes:
 a first current conversion unit which converts the bias voltage into a first converted current; and 
 a first buffer amplifier having an input coupled to an output of the current conversion unit and an output coupled to the output of the first bias control circuit; 
 a first low-pass filter coupled between the output of the first bias control circuit and the base terminal of the first transistor; and 
 a first reference voltage generating unit which receives the first converted current from the first current conversion unit and which generates a first reference voltage based on the first converted current, wherein the first reference voltage is amplified by the first buffer amplifier and is provided to the first low-pass filter, 
 
 wherein the first current conversion unit comprises:
 an op amplifier having a voltage follower configuration; 
 a first MOS transistor which has a gate connected to an output portion of the op amplifier and which is coupled in series between a power supply voltage and a reference potential to generate a first current; and 
 a second MOS transistor whose gate is coupled to the output portion of the op amplifier and which is coupled in series between the power supply voltage and the first reference voltage generating unit to generate a second current of the same level as the first current, and 
 
 wherein the first buffer amplifier includes a voltage follower-coupled op amplifier. 
 
     
     
       2. The high frequency power amplifier module according to  claim 1 , further comprises:
 a second transistor which is coupled to the base terminal of the first transistor and performs current amplification in response to an input signal received at a base terminal thereof, the base terminal thereof being biased based on a second bias control signal; 
 a second bias control circuit which generates the second bias control signal supplied to the base terminal of the second transistor; 
 a second low-pass filter coupled between an output of the second bias control circuit and the base terminal of the second transistor; and 
 a second reference voltage generating unit which generates a second reference voltage from a second converted current, 
 wherein the second bias control circuit includes:
 a second current conversion unit which converts the bias voltage into the second converted current; and 
 a second buffer amplifier which amplifies the second reference voltage generated by the second reference voltage generating unit and provides the amplified voltage second reference voltage to the second low-pass filter. 
 
 
     
     
       3. The high frequency power amplifier module comprising:
 a first transistor which performs current amplification in response to an input signal received at a base terminal thereof, the base terminal being biased based on a first bias control signal; 
 a first bias control circuit having an input which receives a bias voltage and an output which generates the first bias control signal, wherein the first bias control circuit includes;
 a first current conversion unit which converts the bias voltage into a first converted current; and 
 a first buffer amplifier having an input coupled to an output of the current conversion unit and an output coupled to the output of the first bias control circuit; 
 a first low-pass filter coupled between the output of the first bias control circuit and the base terminal of the first transistor; and 
 a first reference voltage generating unit which receives the first converted current from the first current conversion unit and which generates a first reference voltage based on the first converted current, wherein the first reference voltage is amplified by the first buffer amplifier and is provided to the first low-pass filter, 
 
 wherein the first low-pass filter includes:
 an inductance coupled in series between the output portion of the first bias control circuit and the base terminal of the transistor; and 
 an electrostatic capacitive element coupled between the inductance and the reference potential, and 
 
 wherein the inductance is formed of bonding wires. 
 
     
     
       4. The high frequency power amplifying module according to  claim 2 , wherein input portions of the first and second bias control circuits are commonly coupled and inputted with the bias voltage in common. 
     
     
       5. The high frequency power amplifier module according to  claim 1 , wherein the first low-pass filter is provided at an input-side terminal of an op amplifier in the first buffer amplifier. 
     
     
       6. The high frequency power amplifier module according to  claim 1 , wherein the first transistor includes a plurality of transistors parallel-connected to one another. 
     
     
       7. The high frequency power amplifier module according to  claim 2 , wherein the second transistor includes a plurality of second transistors parallel-connected to one another. 
     
     
       8. The high frequency power amplifier module according to  claim 1 , wherein the first transistor is a GaAs HBT. 
     
     
       9. The high frequency power amplifier module according to  claim 2 , wherein the second transistor is a GaAs HBT. 
     
     
       10. The high frequency power amplifier module according to  claim 3 , further comprising:
 a second transistor which is coupled to the base terminal of the first transistor and performs current amplification in response to an input signal received at a base terminal thereof, the base terminal thereof being biased based on a second bias control signal; 
 a second bias control circuit which generates the second bias control signal supplied to the base terminal of the second transistor; 
 a second low-pass filter coupled between an output of the second bias control circuit and the base terminal of the second transistor; and 
 a second reference voltage generating unit which generates a second reference voltage from a second converted current, 
 wherein the second bias control circuit includes:
 a second current conversion unit which converts the bias voltage into the second converted current; and 
 a second buffer amplifier which amplifies the second reference voltage generated by the second reference voltage generating unit and provides the amplified voltage second reference voltage to the second low-pass filter. 
 
 
     
     
       11. The high frequency power amplifier module according to  claim 3 ,
 wherein the first current conversion unit includes:
 an op amplifier having a voltage follower configuration; 
 a first MOS transistor which has a gate connected to an output portion of the op amplifier and which is coupled in series between a power supply voltage and a reference potential to generate a first current; and 
 a second MOS transistor whose gate is coupled to the output portion of the op amplifier and which is coupled in series between the power supply voltage and the first reference voltage generating unit to generate a second current of the same level as the first current, 
 
 wherein the first buffer amplifier includes a voltage follower-coupled op amplifier. 
 
     
     
       12. The high frequency power amplifying module according to  claim 3 , wherein input portions of the first and second bias control circuits are commonly coupled and inputted with the bias voltage in common. 
     
     
       13. The high frequency power amplifier module according to  claim 3 , wherein the first low-pass filter is provided at an input-side terminal of an op amplifier in the first buffer amplifier. 
     
     
       14. The high frequency power amplifier module according to  claim 3 , wherein the first transistor includes a plurality of transistors parallel-connected to one another. 
     
     
       15. The high frequency power amplifier module according to  claim 3 , wherein the second transistor includes a plurality of second transistors parallel-connected to one another. 
     
     
       16. The high frequency power amplifier module according to  claim 3 , wherein the first transistor is a GaAs HBT. 
     
     
       17. The high frequency power amplifier module according to  claim 3 , wherein the second transistor is a GaAs HBT.